An SUV tucked away in the shadows of the Philadelphia Convention Center's tunnel bears the ubiquitous logo for Google Maps, and mounted on top of the vehicle are two high-powered license plate reader cameras. To the average passerby, it might appear to be a Google street view vehicle.

Others, such as Matt Blaze, a University of Pennsylvania computer and information science professor, saw it for what it truly was: a crudely disguised tool for surveillance. Blaze tweeted a photo of the vehicle with the appropriate opening: "WTF?"

Blaze's baffled pronouncement is appropriate. Why would a government agency need to disguise a surveillance vehicle like this? And which agency believes it needs to do so?

A placard on the dashboard indicates that the SUV is registered with the Philadelphia Office of Fleet Management, which maintains city government's 6,316 vehicles, indicating that the vehicle is being used by a local agency.

Christopher Cocci, who serves as the city's fleet manager, and whose signature is on the document, says that the vehicle does not belong to the Pennsylvania State Police, which is known to use automated license plate recognition (ALPR), or the Philadelphia Parking Authority, a local agency that also utilizes ALPR. So whose surveillance truck is it?

"All city vehicles such as police, fire, streets etc.…are registered to the city. Quasi [public] agencies like PPA, Housing Authority, PGW and School District are registered to their respective agencies," fleet manager Christopher Cocci wrote in an email to Motherboard after reviewing photos of the vehicle. He also believes it to be connected to law enforcement activity.

Unless the Philadelphia Fire Department or Streets Department are using ALPR, this strongly suggests that the city's police department is trawling city streets under the auspices of Google while snapping thousands of license plate images per minute. That's very puzzling, because as of 2011, Philly police have been operating at least 10 mobile camera units and not hiding that fact.

The use of ALPR is controversial because of its ability to photograph thousands of license plate images per minute, and in doing so, warrantlessly track and store the average person's travel habits. In Philly, the police can retain this data for a full year, even though the vast majority of residents are not under investigation. Plate information captured and subsequently used for investigations can be stored indefinitely, according to a department directive.

So why this subterfuge? Two spokespersons with the Philadelphia Police Department were not immediately available for comment.

"We can confirm that this is not a Google Maps car, and that we are currently looking into the matter," Google spokesperson Susan Cadrecha wrote. When pressed, Cadrecha would not elaborate as to whether the company was concerned or angered that a local agency would be using a vehicle with powerful—and controversial—surveillance technology while masquerading as a street mapping car.

In a follow-up email, Cadrecha said: "We don't have any further comment at this time," but indicated that the company might have more to say as their inquiry continues.